Michael Kay asks:
> > As your other reply said, the result of an extension is
> > always a sequence of the extended model followed by the
> > extending model.
> I've had trouble myself in working out how this applies to content
> models that use xs:all.
The short answer is, it doesn't. You can't extend an all group. There's
no coherent reason I'm aware of in principle: we could have let you
extend an 'all' with another 'all'. My recollection of the history is
that some WG members were dubious about having 'all' at all, and for
better or worse that led to a general 'go slow' attitude on making it more
capable. Similar reasoning applies to the lack of minOccurs/maxOccurs on
the constituents of an all group.
It would take a little longer than I have to give links to the exact
component constraints, but basically I believe it's the ones that say (a)
an extension is a sequence that must have as its first member the model
group being extended and (b) an all group must be at the top level. My
reading is that to satisfy the first rule, the all group would have to be
within the extended sequence, and hence not at the top level. QED (more or
less.)
--------------------------------------
Noah Mendelsohn
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------